Various devices have been proposed for detecting the presence of a hospital patient incontinent event, i.e., the presence of urine. Pads have been developed which employ a single electrical circuit within the pad, with a number of moisture-sensitive electrical conductors electrically connected in parallel to the voltage source applied to the circuit. One or more of the moisture-sensitive electrical conductors, upon being moistened by urine, complete the electrical circuit. An alarm has traditionally been wired into the circuit, with the moisture-sensitive conductors being positioned between the alarm and power supply. Hence, when a patient incontinent event occurs, the alarm is activated, apprising a caregiver that the patient should be attended to.
The single circuit type of device which has a number of moisture-sensitive conductors electrically connected in parallel with the voltage source of the device can take one of two forms. One form is as illustrated in Norton U.S. Pat. No. 5,137,033 wherein electrical conductors, for example foil strips, are spaced through the thickness of the pad with fabric separating the strips, such that when the pad is moistened by urine through its depth the circuit becomes complete from the top to the bottom of the pad through the pad.
Another type of device which similarly employs a single circuit with a number of moisture-sensitive electrical conductors electrically connected in parallel to the voltage source of the device is the type which utilizes a single electrical conductor woven back and forth through the pad but within a uniform horizontal plane of the pad. In this type of device the voltage source is applied to the two ends of the conductor, but the conductor is an "open" circuit as there is a break in the conductor somewhere along its path. The conductor is woven such that adjacent points of the electrical conductor are within, for example, approximately one inch of each other. When fabric between adjacent points of the conductor becomes moistened the circuit becomes complete. This type of device is shown, for example, in Kelly et al U.S. Pat. No. 4,539,559.
In neither of these two types of devices, that is, the type employing moisture-sensitive conductors spaced through the pad thickness, or the type having conductors spaced across the width and length of the pad in a uniform plane, is the device able to discriminate between incontinent events of varying volumes. That is to say, an incontinent event, of any liquid volume, as long as the urine therefrom is positioned in the appropriate position on the detecting pad, will activate the device and hence notify the caregiver that the patient is to be attended to. Thus, the caregiver is notified that the patient needs to be attended to, whether the incontinent event is 30cc's or 300cc's, the former ordinarily not requiring immediate care, while the latter may do so. Accordingly, these types of devices are subject to so-called "nuisance" readings, wherein a very small incontinent event will trigger the device indicating that the patient requires care by a caregiver, whereas in fact it would not be paramount that the patient receive care at that time.
With respect to the type of device employing the moisture-sensitive conductors through the thickness of the pad, varying the lateral spacing of the conductors essentially has no effect on the "resolution" of the device, as long as the urine, no matter how small the volume, is centered over one of the conductors. Therefore, the device could be triggered by either a 30cc event or a 300cc event. With respect to the other type of device employing the moisture-sensitive conductors within a common plane, increasing the linear distance between adjacent points on the conductor will desirably decrease the resolution of the device so as to avoid nuisance alarms; however, as in the former device there is no means by which to discriminate for varying volumes of the incontinent event.